Finished FUBAR last night & tbh, I found my first playthrough harder because I tried to be gung-ho, and didn't use my AI buddies well & didn't work out a strategy for beating Juggernauts. Man I died like a million times...
2nd play was different. As these guys have said remember:
Patience, Prioritisation, Patterns & Covering fire
Sit tight in cover & 9/10 you'll be fine. Just make sure you know where to go if a grenade gets thrown
Priortise deadly targets like snipers or shotgunners. The AI is ALWAYS the same. Figure out the pattern & it's a turkey shoot with snap aim. Pop up quick and burst fire (AK47 was my choice) rinse & repeat.
If your AI is going down too easy you're probably picking the wrong targets that are too far away, or not giving them enough covering fire. Make sure you take out any target firing at them. Use them to distract an enemy & get their attention then pop up & kill them. Think of them as aggro magnets (like Army of 2) and use them to get the AI to pop out of cover & fire. I know the AI is flakey, but on Lvl 14 my AI buddy never died because I killed any soldier that was shooting at him.
BTW - Thanks for all the great FUBAR tips guys. I came close to quitting a few times, and had some major rages at times, but I knew I could beat it...